Salzburg Airport: Take the direct Bus 260 to Zell am See Postplatz when its timetable works: about 1 hr 45 min and roughly €10–14. It is the sensible public-transport transfer because it avoids dragging bags via Salzburg Hauptbahnhof. There are also taxi/van transfers; expect about €120–150 per vehicle, which only makes sense for a full group.
Salzburg Hauptbahnhof: ÖBB trains to Zell am See run about hourly and take around 90 minutes; budget roughly €20–25 one way on a standard flexible fare. Zell am See Bahnhof is in the centre, a short walk from the lakefront and old town—do not pay for a resort transfer from the station unless your hotel is well outside town.
Zell am See Bahnhof: This is the arrival point to aim for, not an out-of-town station: it sits beside the historic centre and lake. It has direct rail links toward Salzburg and Tirol/Innsbruck; use it as the base for local buses to Kaprun and the ski lifts.
Zell am See Airport: This is a small aviation airport about 3.5 km south of town, not a practical scheduled-airline gateway. If you arrive by private or charter flight, take a local taxi; otherwise walk to nearby Bruckberg im Pinzgau station only if travelling light and weather is decent.